Work vehicles (and other vehicles) may usefully be equipped with multi-speed transmissions, including, for example, transmissions with multiple ranges and speeds. Operators of such vehicles may select the appropriate speed (or range or gear) for a particular task (or may have it selected on their behalf, such as by various computing systems included in the vehicles), based upon considerations that may include the desired wheel speed, the torque required for a particular operation, and so on. In certain configurations, a transmission may include multiple clutches (e.g., friction clutches) associated, respectively, with various gears and rotating shafts (e.g., an input shaft, an output shaft, various countershafts, and so on). Accordingly, changes between speeds (or ranges or gears) may be effected, at least in part, through the actuation of one or multiple clutches. In many transmission systems, various shifting operations (i.e., changes among gears or ranges or speeds, and so on) may require particular transitions between clutches. In certain configurations, particular shifting operations may require transitions for clutches of various clutch sets (e.g., in a tractor, a transition from a “high” direction clutch to a “low” direction clutch, along with a transition from a first speed clutch to a second speed clutch).
Notably, under traditional strategies for control of shifting operations, the implication of multiple clutches in many possible shifting operations may lead to significant complexity. This is because traditionally control of complex transmissions has included a significant empirical element, particularly in the calibration of electrical current (or pressure) commands issued by the clutch controller (e.g., a hardwired controller or a software-embodied method executed by a transmission control unit (“TCU”)) to a clutch valve. For example, a 23-speed tractor transmission may include ten clutches, implicating hundreds of distinct shifting operations. It has not been practical, however, to implement general control profiles, in part due to the difficulty in applying generalized current signal (or pressure) profiles to particular clutches (or clutch combinations). For example, although a 4 bar/sec pressure ramp-up rate may be found to be appropriate for one clutch in one shifting operation, 4 bar/sec (or another value easily derived therefrom) may not necessarily be appropriate for another clutch configuration or another shifting operation. As such, a particular current signal profile is typically determined empirically for each shifting operation of a transmission. Further, changes in various external factors (e.g., ambient temperature), variation in actual clutch performance from nominal or tested performance (e.g., due to clutch wear or defect), and other factors can require significant changes to clutch control strategies, thereby increasing the time and effort required for calibration (i.e., for determining each of the various parameters required to shift a transmission, including offsets, timing, and clutch ramp rates). As such, calibration of complex transmissions may sometimes require extensive empirical testing over many months.